CONTROL STRATEGY TO PREVENT HUMIDITY CYCLING IN A FUEL CELL
First Claim
Patent Images
1. A fuel cell system comprising:
- a fuel cell stack;
a power source; and
a controller, responsive to a power request signal, said controller including a damping filter that damps the power request signal over a damping time during a low power transient and provides a damped power demand signal to the fuel cell stack that provides more power than the power request signal during the damping time.
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Abstract
A system and method for reducing RH cycling of the membranes in a fuel cell stack. A control algorithm damps a power request signal using a first order filter during low power transients so that the fuel cell stack continues generating power at a higher rate than is requested. The excess power generated by the stack is used to recharge a battery in the fuel cell system. The damped power signal is weighted so that more fuel cell stack power is provided for a low battery state of charge unless stack power is provided for a high battery state of charge.
4 Citations
27 Claims
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1. A fuel cell system comprising:
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a fuel cell stack; a power source; and a controller, responsive to a power request signal, said controller including a damping filter that damps the power request signal over a damping time during a low power transient and provides a damped power demand signal to the fuel cell stack that provides more power than the power request signal during the damping time. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A hybrid fuel cell system comprising:
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a fuel cell stack; a battery; and a controller responsive to a power request signal and a battery state of charge signal, said controller including a damping filter that damps the power request signal over a damping time during a low power transient and provides a damped power demand signal that provides more power than the power request signal during the damping time, said controller further including a state of charge weighting factor look-up table that provides a multiplier factor depending on the battery state of charge, said controller multiplying the weighting factor by the damped power demand signal to increase or decrease the damped power demand signal depending on the state of charge of the battery, wherein excess power generated by the fuel cell stack above the power request signal is used to charge the battery. - View Dependent Claims (11, 12, 13, 14, 15)
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16. A fuel cell system comprising:
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a fuel cell stack; a compressor providing a cathode air flow to the fuel cell stack; a flow meter for measuring the flow of the cathode air from the compressor to the fuel cell stack; and a controller for controlling the output power of the fuel cell stack during low power transients, said controller providing a command to the compressor to provide the air flow required for a desired current density that provides a desired power request, said controller further calculating a cathode feedback stoichiometry based on the desired current density and the flow of air through the flow meter, said controller further calculating an intermediate current density that will maintain the cathode stoichiometry at a set-point for the desired current density, and said controller causing the fuel cell stack to generate the intermediate current density. - View Dependent Claims (17, 18, 19, 20)
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21. A method for providing a power demand signal to a fuel cell stack in a fuel cell system, said method comprising:
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operating the fuel cell stack at a higher power than a desired power request during a low power transient; and using the excess stack power to charge a battery. - View Dependent Claims (22, 23, 24, 25, 26, 27)
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Specification